Inspector Imanishi Investigates is well-paced, but its plot is fairly linear, tracking Imanishi as he follows up one clue after another — some of them a little too neatly dropped in his lap, through coincidences involving his wife and sister and their connections. He is a likeable character, with a happy domestic life and a hobby growing bonsai, but is most notable for his persistence. And his off-sider Yoshimura is really just a foil, with a very minor role.
Some chapters describe events outside Imanishi's knowledge, which means the reader always has more information than the detective, but there are still some surprises. The main interest, however, is not in those but in the unfolding of the investigation. And Japan in 1960 provides a striking setting: the railways, rural poverty, Japanese dialects, the damage from bombing in the war, social status and prejudice, and more all feature.